The goal of this project is elucidation of the molecular events involved in expression and control of a eucaryotic gene. We are using the genes coding for the last two enzymes of allantoin degradation in Saccharomyces cerevisiae (urea carboxylase and allophante hydrolase) as our model. We have shown that induction of allophanate hydrolase involves 2 processes: synthesis of a specific synthetic capacity which is likely a messenger RNA and expression or translation of the synthesized capacity. The times at which RNA synthesis, rnal gene product function, protein synthesis initiation and termination occur during the induction lag period have been determined. We have shown that there exists at least two major classes of messenger RNA in yeast. One class that is labile and a second that is 5 to 7 times as stable. To avoid confusing mutations causing defects in uptake of allantoin related compounds with those of control elements, we have obtained mutant strains that are defective in these uptake systems. With these mutants we can demonstrate the existence of 4 uptake systems: one each for allantoin and allantoic acid and two for urea. With the genes responsible for both the pathway enzymes and uptake systems identified, a search was mounted for mutant strains possessing defective control elements. Three major classes of mutants that are presumptively defective in the regulation of the pathway have been isolated. Using these results as a basis, we propose to pursue the following areas of study: (1) characterization of temperature sensitive mutant strains which cannot execute macromolecular biosynthetic functions needed for induction of allophanate hydrolase; (2) demonstration that induction of allophanate hydrolase involves production of a specific messenger RNA transcribed from the allophanate hydrolase structural gene; (3) identification and sequencing of the macromolecular biosynthetic events involved in the induction of urea carboxylase; (4) determination of the mechanisms involved in regulation of the allantoin degradative system; and (5) isolation and characterization of mutant strains that have pleiotropically lost their ability to metabolize a variety of nitrogenous compounds.